How can we tell the difference between gases like hydrogen, oxygen, and carbon dioxide cause they all look to same?

The critical chemical difference is that CO2 contains one atom of carbon and two atoms of oxygen, whilst CO has one carbon and one oxygen atom.

state the principle of separating two immiscible liquids by separating funnel. describe an activity with diagram to separate a mixture of water and kerosene oil. answer: immiscible layers separate out in layers depending on their densities in separating funne

it is the most commonly accepted one